Products/members having a resin film surface have been used in wide fields and they have been used after processed to have respective functions, depending on their intended use. In general, their surface however shows hydrophobicity/lipophilicity due to original properties of the resins. When oils and the like attach to such a surface as dirt, they cannot be removed easily. Accumulation of oil and the like sometimes extremely deteriorates the functions/properties of the products/members having such a surface. On the other hand, when products/members having a transparent function are exposed to high-humidity conditions or falling rain, water droplets attached thereto cause diffuse reflection and inhibit light transmission. Similarly, products/members having an inorganic surface such as glass or metal exhibit neither sufficient antifouling properties against dirt such as oil attached thereto nor sufficient antifogging properties when water droplets attach to thereto. In particular, there is an eager demand for the development of glass for automobiles or building materials having antifouling properties or antifogging properties, because hydrophobic contaminants, e.g., combustion products such as carbon black contained in a dust from urban areas or exhaust gas from automobiles, oils or fats, and components released from sealants adhere to the glass or water droplets adhere to the glass and hinder the vision through the glass (reflection in the case of a mirror).
Supposing from the viewpoint of the antifouling property that the dirt is an organic substance such as oil, it is necessary to reduce the interaction between the dirt and the surface of the material, in short, to make the surface hydrophilic or oil-repellent in order to prevent the surface from being contaminated. With regards to the antifogging properties, it is necessary to impart, to the surface of products/members, extended wettability (namely, hydrophilicity) for spreading attached water droplets uniformly on the surface or water repellency such that attached water droplets can be removed easily. Accordingly, antifouling/antifogging materials under investigation may tend to rely on hydrophilization or water repellency or oil repellency.
Surface treatment for hydrophilization heretofore proposed, for example, etching treatment or plasma treatment enables high-level surface hydrophilization, but its effect is temporary and the hydrophilic state cannot be kept for a long period of time. There is also proposed a surface-hydrophilic coating film using a hydrophilic graft polymer as one of hydrophilic resins (refer to, for example, Non-patent Document 1). According to this report, this coating film has hydrophilicity to some extent, but is required to have higher durability because it has only insufficient affinity to substrates.
For another member having a surface hydrophilic function, use of titanium oxide as a photocatalyst has conventionally been known. This utilizes an oxidative decomposition function and a hydrophilization function of an organic substance due to exposure to light. For example, it is disclosed that when a photocatalyst-containing layer is formed on the surface of a substrate, the surface is made highly hydrophilic, depending on the optical excitation via the photocatalyst. It is reported that when this technique is applied to various composite materials such as glass, lenses, mirrors, exterior materials and water supply members, it may give excellent antifogging and antifouling functions to these composite materials (refer to, for example, Patent Document 1). Although members obtained by applying titanium oxide onto a glass surface have been used, as a self cleaning material, for windowpanes of building materials or front glass of automobiles, exposure to sun light for long hours is necessary for them to exhibit functions such as antifouling properties and antifogging properties. Deterioration of their properties due to dirt accumulated with the passage of time is inevitable. In addition, since they do not have sufficient film strength, they need improvement in durability. Self cleaning films obtained by forming a titanium oxide layer on a plastic substrate have been used for side mirrors of automobiles, but their film strength is also insufficient so that hydrophilic materials having better wear resistance are required.
To solve the above-mentioned problems, an attention was paid to the properties of a sol-gel organic-inorganic hybrid film and it has been found that a hydrophilic surface having a crosslinked structure formed through hydrolysis and polycondensation of a hydrophilic polymer and an alkoxide exhibits excellent antifogging properties and antifouling properties and at the same time, has good wear resistance (refer to, for example, Patent Document 2). The film is desired to have further improved adhesion properties.
On the other hand, with regards to coating compositions, there is proposed a curable composition containing a copolymer component composed of a hydrolyzable-silyl-containing vinyl monomer, an alcoholic-hydroxyl-containing vinyl monomer, and a tertiary-amino-containing vinyl monomer. The composition is suited for top coat of automobiles because it has good acid resistance, water resistance, and weather resistance (refer to, for example, Patent Document 3). A coating composition containing a hydrolysate or partial condensate of an organosilane and a vinyl copolymer is proposed and a film excellent in weather resistance and contamination resistance can be obtained using the composition (refer to, for example, Patent Document 4). Films available using these coating compositions are however lipophilic and have low antifogging properties. In addition, they are limited in antifouling properties. There is therefore a demand for further improvement of antifogging properties and antifouling properties.
A heat exchanger of an air conditioner is formed of a pipe for transferring a heat medium and a fin for absorbing heat in the air or diffusing heat from the heat medium. In a room air conditioner, a copper pipe is penetrated through fin stocks, that is, thin aluminum plates having a thickness of about 0.1 mm. With regard to fin stocks, cohesive water generated during cooling becomes water droplets and remain between fins. Water bridges formed by them reduce the cooling capacity and dusts attached between fin stocks also deteriorate the cooling capacity.    Patent Document 1: WO96/29375    Patent Document 2: Japanese Patent Laid-Open No. 2002-361800    Patent Document 3: Japanese Patent No. 3412916    Patent Document 4: Japanese Patent Laid-Open No. Hei 10-273623    Non-patent document 1: The Chemical Daily, Jan. 30, 1995